Reversing Switch Design for Load Tap Changer Heat Mitigation

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Solution Overview

Problem

Conventional reversing switches in load tap changers are prone to heating and coking, leading to frequent replacements and increased costs due to transformer outages and failures.

Innovation Solution

A new reversing switch design featuring a rotatable post, contact structures, and a movable contact arm with a contact assembly that includes inward and outward contacts, along with a bus bar connecting a third contact structure to a neutral terminal, allowing for improved electrical connections and reduced heat buildup, and a method for retrofitting existing load tap changers with these components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional reversing switches are used in load tap changers, then the device can perform polarity switching, but the switch contacts are prone to heating and coking leading to frequent failures

Engineering Contradiction:

Improvereversing switch reliabilityVSAvoidheating and coking

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The reversing switch is divided into separate functional components: a rotatable post for positioning, a movable contact arm for switching, and stationary contact structures. This segmentation allows each component to be optimized independently, reducing heat concentration and improving reliability by distributing thermal loads across multiple elements rather than concentrating them in a single switch mechanism.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The contact arm is extracted as a separate movable component that can be independently positioned and replaced. By taking out the contact arm from the traditional integrated switch design, the patent allows for easier maintenance and replacement of worn contacts, thereby improving overall reliability without requiring complete switch replacement.

Inventive Principle:

Principle #2Taking out (Extraction)

2Ease of manufacture

If conventional reversing switches are used, then polarity switching is achieved, but frequent replacements increase maintenance costs and transformer outages

Engineering Contradiction:

Improvemaintenance costVSAvoidreversing switch lifespan

Core Design Contradiction:

Ease of manufactureVSDuration of action of stationary object

Solution Approach 1:

The contact arm is designed as a dynamic, movable component that can be independently actuated and replaced. This dynamic design allows for selective replacement of only the worn contact arm rather than the entire reversing switch assembly, extending the overall lifespan of the reversing switch mechanism and reducing maintenance costs.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent incorporates design features that allow for preliminary replacement of contact arms before complete failure occurs. The modular construction enables easy identification and replacement of worn contacts, preventing catastrophic failures and extending the operational lifespan of the reversing switch assembly.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If the reversing switch is redesigned with separate contact structures, then reliability improves, but device complexity increases

Engineering Contradiction:

Improvereversing switch reliabilityVSAvoidreversing switch structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The rotatable post serves multiple functions: it positions the contact arm, provides mechanical support, and enables the switching action. This multi-functionality reduces the need for separate components, thereby improving reliability through better load distribution while minimizing the increase in overall device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent combines the mounting structure and contact support functions into the rotatable post assembly. By merging these functions into a single integrated component, the design achieves improved reliability through better structural integrity while avoiding excessive complexity that would result from completely separate mounting and switching mechanisms.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS8207457B2Reversing and a method of modifying a tap changer to use the same

Publication Date: 2012.06.26 HITACHI ENERGY LTD

AI summary

A reversing switch for a tap changer of a transformer is provided. The reversing switch includes first and second contact structures for connection to a winding of the transformer and a mounting structure for connection to a neutral terminal of the transformer. A bus bar connects a third contact structure to the mounting structure. A movable contact arm is secured to a rotatable post. The contact arm includes a contact assembly mounted to an arm. The contact assembly has one or more outward contacts and one or more inward contacts. The one or more inward contacts engage the third contact structure and the one or more outward contacts selectively engage the first contact structure or the second contact structure. The first and second contact structures and the mounting structure are located at about the same radial distance from the post, while the third contact structure is located closer to the post.